Stepper motor for makerslide

[Gilles]

Good morning,


I bought everything i need to make my makerslide motorized slider except for the stepper motor.
i suppose it's the nema 17 you used, but the thing is that i'm not sure it will be enough to support my camera and camera rig ( approximatively 3-4 kg )
Someone suggest me this stepper motor http://www.robotshop.com/eu/productinfo.aspx?pc=RB-Phi-132&lang=en-US

But i think i won't be able to screw it on your plate...
Can you advise me ??
Maybe the nema 17 will be enough, but i'm really beginner on this.
Or the nema 23, but i will have to make an other support plate for the stepper motor ( because it's bigger ) ...

Thanks a lot for all your answers !!!

Best

[bdring]

That seems like a pretty big camera rig for a makerslide based slider. What acceleration do you need? What is the maximum angle the camera needs to climb?

[Cre8ivdsgn]

Bart's right. We need to know a bit more about what it is you are doing. The load by itself isn't the issue. The questions are: what is the peak velocity you want to achieve and what is the acceleration you need to achieve that velocity (and even here we are presuming the acceleration and deceleration issues are the same which is only true for a horizontal axis). FInally we need to know the orientation or we might assume horizontal.
But bart said that... in fewer words too! Time for another cup of coffee....

[flurin]

Maybe the nema 17 will be enough, but i'm really beginner on this.

Smart Automation Nema 17, SM42HT47-1684A:
Max radial force 28N
Max axial force 10N

[Gilles]

Thanks for your answer.

To tell you more about my rig : it's a 5dmark2 with lens and an emotimo TB3 for the pan and tilt http://emotimo.com/index.php?option=com_content&view=article&id=46&Itemid=27
I'm doing stop motion, so i don't need velocity, my principal demand is accuracy.
I will certainly have only horizontal move with my slider, or really small angle

[Gilles]

That's why they suggest me the stepper i show you on the link above.
As i understand, it's better for me to have a gear ratio around 25:1 and a low RPM ( even if i don't fully understand what that represent )

My concern will be to have stepper motor able to move my rig and enough accurate for stop motion.

[Cre8ivdsgn]

I wrote a long reply with great info, but for some reason the system logged me off!!! I lost all the stuff I entered with formulas.

I ran through the calculations and even put a 10lb load on a three wheel trolly on MakerSlide, which gave a <10oz friction force component. Because speed and acceleration are not an issue (only friction component of torque amounts to anything), I got something like 2.55 oz inches of torque to move the load.

Adding a modest speed component of .05" moves at 1 second profile move time, I only added 0.28 oz-inches of torque. So basically 2.83 oz inches of torque or 203 g-cm. A NEMA 17 motor with a 20 tooth pulley or less should easily be capable of moving the load.

You can figure out the forces by following here: http://www.leadshine.com/Pdf/Calculation.pdf
I liked parker compumotors literature a bit better. Lin Engineering and Danaher both have motion calculators.

[cvoinescu]

A 70 oz in motor with an 18-tooth MXL pulley (abut 5.8 mm pitch radius) will be able to exert a force of about 87 N (8.6 kgf) on the belt. That's enough to hold a 4 kg rig on a vertical rail and move it slowly up or down, with very gentle acceleration. However, the radial force spec for the motor is only about 30 N, which means you'll exceed that by a factor of two (or more, depending on how the belt is routed). I don't think the shaft will break; you'll just wear the bearings much faster, which is something I wouldn't worry about in your application.

However, it seems that a NEMA17 is marginal. I'd go with a NEMA23. It costs only a little more, 1/4" bore pulleys are available too, and you can still use the same drivers. A small NEMA23 (e.g. 50 mm long) weighs only about 500-600 g (less than twice as much as a large NEMA17) and provides at least 125 oz in of holding torque, so I think it's just right.

Even better would be a NEMA17 motor with a gear box. You mention 25:1, which sounds perfectly fine. It may give you some additional positioning accuracy (which you may or may not need, and backlash from the gears may negate any gain), and definitely plenty of torque to move your rig. It won't be fast, though, but then neither would the non-geared NEMA17. An important advantage of a geared motor is that, with a vertical rail, if power to the driver gets cut (or the driver overheats and shuts down), the detent torque of the unpowered motor may hold your rig up, and even if it doesn't, friction and electromagnetic braking (involving the protection diodes in the driver circuit) would slow down its fall. With an non-geared motor, the moment you turn the power off, the rig falls all the way down (not free-fall, but if the stop is not a shock absorber, it's still a hard bump).

[Gilles]

So a nema 17 should be ok or not ? Because it's seams that i have two differents answers

cvoinescu, i found a 64oz nema 17 http://www.stepperonline.com/3d-printer-nema-17-stepper-motor-2a-45ncm64ozin-17hs162004s-p-16.html. Do you think it's the solution ?

By the way , i know that a geared motor ( nema 17 ) will be perfect, but i was wondering if it will be fixed and hold correctly ( because of the gear ) and if i will find correct screws for that... But maybe i'm asking too many questions, and that will just work fine ...

[Gilles]

or maybe this one : http://www.stepperonline.com/nema-17-bipolar-stepper-motor-65ncm92ozin-21a-17hs242104s-p-21.html